The epidemiology of E. coli O157 in Scotland

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The epidemiology of E. coli O157 in Scotland
tip of the iceberg?

• Kevin Pollock

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Health Protection Scotland

• "to improve the health of the Scottish
  population by providing the best possible
  information and expert support to practitioners,
  policy-makers and others on infectious and
  environmental hazards."
• www.hps.scot.nhs.uk

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Why am I here?

• Central Scotland E. coli O157 outbreak (1996)
• 512 cases (279 lab-confirmed)
• 34 cases of HUS
• 17 deaths
• E coli O157 Task Force report
• Creation of a surveillance system for E. coli
  O157 and HUS to include both children and adults

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What is surveillance?

• the ongoing systematic collection, analysis and
  interpretation of appropriate data, and the
  timely dissemination of the resultant information
  to those who need to know
• adapted from Langmuir AD. The surveillance of
  communicable diseases of national importance. New
  England Journal of Medicine, 1963, vol 268, pp
  182-192

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Factors which affect surveillance

• Laboratory testing policies
• Notification vs reporting
• Anthrax vs Campylobacter
• Clinician bias to pathogens
• Enhanced surveillance

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Epidemiology

• The study of the distribution and determinants
  of health-related states or events in specified
  populations and the application of this study to
  control health problems
• Human disease does not occur at random
• Human disease has causal and preventive factors
  that can be identified through systematic
  investigation of different populations or
  subgroups of individuals within a population in
  different places or at different times

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Laboratory Surveillance
Appears in national surveillance
Organisms identified
Specimens sent
Cases presenting
Cases of illness
Cases of infection
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Lab reports and under-ascertainment

• The study of IID in England (1996) showed factor
  is
• 3.8 for salmonella
• 10.3 for campylobacter
• 22.5 for rotavirus
• 315 for norovirus
• i.e.
• if there were 1400 reported cases of norovirus in
  2005 then Scotland experienced 315 x 1400
  441,000 cases

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E. coli O157

• Gram (-) rods, usually sorbitol-fermenting, part
  of the VTEC family
• Reservoir cattle/livestock/humans
• Can exist in a VBNC state problems with
  detection
• Abdominal cramps, bloody diarrhoea, afebrile
• May develop into the haemolytic uraemic syndrome
  in 10-15 of cases resulting in kidney failure
  and possible death
• Patients should not be treated with antibiotics

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E.coli O157 NHS Board of Reporting Laboratory
2007
Shetland 0.0
Orkney 15.4
Western Isles 0.0
Highland 0.9
Grampian 9.0
Tayside 3.6
Fife 2.0
Argyll Clyde 4.6
Forth Valley 2.1
Greater Glasgow 0.8
Lothian 2.8
Lanarkshire 1.4
Borders 8.2
Ayrshire Arran 3.8
Dumfries Galloway 9.5
Scotland 3.4
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E.coli O157 rates per 100,000 population
1984-2007
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E. coli O157/HUS in children
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E. coli O157/HUS in adults
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Progression of E. coli O157 (VTEC)
Tarr et al. 2005, Lancet 365 1073-1086.
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How important?

• Of 200-300 reported cases per year in Scotland
• 2-3 die
• 80-85 are sporadic infections
• 70 have bloody diarrhoea
• 50 are admitted hospital
• 20 are in hospital for over a week
• 10-15 have HUS (20-35 cases)
• 90 of HUS cases are under 16
• Potential for devastating outbreaks.

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Recent selected outbreaks

• 1996, Scotland, butcher
• 512 cases, 17 deaths
• 1996, Japan, school meals
• 10,000 cases, 11 deaths
• 2000, Canada, mains water
• 1300 cases, 6 deaths
• 2005, Wales, school meals
• 158 cases, 1 death

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The Microbiological Safety of Food Part II 1991
We see poultry and their products as the most
important source of human gastrointestinal
infections arising from food.
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Spinach outbreak, USA, 2006

• Cases of E. coli O157 in 26 different states in
  USA reported eating fresh spinach (95 of cases)
• 183 cases
• 92 hospitalised
• 29 had HUS
• 1 person died
• E. coli O157 with a PFGE pattern matching the
  outbreak strain isolated from three open packages
  of fresh spinach consumed by cases (1 from New
  Mexico, 1 from Utah, and 1 from Pennsylvania)
• Spinach grown in California was implicated in the
  outbreak same strain found in feral swine nr
  spinach fields

Jay et al. Emerg Infect Dis. 2007
Dec13(12)1908-11.
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The power of PFGE

• Pulsed field gel electrophoresis
• PulseNet
• Standardized molecular sub-typing (or
  fingerprinting) of foodborne disease-causing
  bacteria
• Allows for rapid comparison of
• patterns and identifies foodborne diseases early
• Importance of stool testing and food testing
• Helps FSA identify areas where implementation of
  new measures are likely to increase the safety of
  our food supply

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Morrisons outbreak, Paisley - 2007

• 9 cases associated with meat delicatessen
• All cases confirmed phage type 2
• 1 fatality - 66-year old female
• No other cases associated with consumption of
  cold cooked meats from Morrisons UK-wide
• Hypothesis - cross-contamination of various cold
  cooked meats at the particular delicatessen
• Fatal accident enquiry

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Aberdeen outbreak, 2007

• 9 confirmed cases associated with hotel and
  social club
• 1 case hospitalised
• EHOs investigated kitchen and routines
• Microbiological sampling of foodstuffs including
  cold cooked meats, coleslaw, salad leaves
• All samples negative for E. coli O157
• 7 out of 10 people from club consumed cold meat
  platter
• Descriptive epidemiology estimates salad part of
  platter as being suspect vehicle previously
  washed in salted water now washed in
  disinfectant solution
• PFGE not used hence descriptive

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Unpasteurised cheese

• Precedent of Listeria in Lanark Blue
• Are all unpasteurised cheeses labelled so?
• Cheese boards in restaurants labelling?
• Cluster of cases of haemolytic uraemic syndrome
  due to unpasteurised cheese
• Deschenes et al. (1996) Pediatr Nephrol, 10

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How are the VTECs being transmitted?

• 50 of cases unknown transmission
• EHO reports of farm contact (plt 0.001)
• EHO reports of person-person spread (plt 0.001)
• Small no. of reports of food as source of
  infection (pre-2007) not statistically
  significant
• Private water supplies theoretical but actual?

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Haemolytic uraemic syndrome (HUS)

• Characterised by microangiopathic haemolytic
  anaemia with red blood cell destruction and fever
• Variable neurological involvement
• Variable renal impairment
• Acute onset, often fatal and difficult to
  diagnose
• 85-90 cases associated with VTEC

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Aims of ENSHURE

• Clinically driven system
• Combines info on short-term and long-term
  outcomes, clinical management and treatment of
  HUS/TTP
• Provides data to enable future prevention and
  management including
• Epidemiology
• Clinical parameters
• Social outcomes of infection

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Clinical markers for HUS and TTP
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Treatment and initial outcomes of HUS

• Treatment of HUS cases with NSAIDs sig.
  associated with renal impairment and death (plt
  0.001)
• Treatment of HUS cases with antibiotics sig.
  associated with dialysis dependence (plt 0.03)
• 71 recovered
• 14 had renal impairment
• - half of these are dialysis-dependent
• 8 had neurological impairment
• 7 deaths

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How did the illness affect patients/relatives?
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How did the illness affect patient/relatives?
Recurring Themes (Initial/1 year follow Up)
Physically exhausting V strict toilet
regime Eating habits change Child has OCD White
coat syndrome Moved to urban area Wary about
hygiene
Association between syndrome and reasons why
developed Inability to absorb information
Diagnosis of illness and explanations
Psychological trauma Mentally exhausting Psycholog
ical and emotional impact on mother Coping levels
stretched
Want written info at time of HUS verbal info
not taken in due to trauma Something on hard
copy More info on HUSH charity GPs should have
more info
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Conclusions

• VTEC/HUS surveillance less artefactual enhanced
  system
• Farm/rural contact important mode of transmission
  of VTEC
• Foodborne E. coli O157 still poses a public
  health threat
• Ready-to-eat produce unlikely source of infection
• Severity of HUS illness and psychological effects
  upon family are devastating
• Vigilance over potential sources for testing -
  PFGE

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